Nitrilotriacetic acid

Structural formula
General
Surname	Nitrilotriacetic acid (NTA)
other names	Tris (carboxymethyl) amine N , N -bis (carboxymethyl) glycine Complexone I. Titriplex I Chelaplex I.
Molecular formula	C 6 H 9 NO 6
Brief description	colorless crystals
External identifiers / databases
CAS number 139-13-9 EC number 205-355-7 ECHA InfoCard 100,004,869 PubChem 8758 ChemSpider 8428 DrugBank DB03040 Wikidata Q425340
properties
Molar mass	191.14 g mol −1
Physical state	firmly
Melting point	241.5 ° C (decomposition)
pK s value	pK S 1 : 1.9 pK S 2 : 2.5 pK S 3 : 9.7
solubility	heavy in water (1.28 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 351-319 P: 280-305 + 351 + 338-308 + 313
Toxicological data	1100 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Nitrilotriacetic acid, or NTA for short, is a complexing agent . In aqueous solution, NTA forms stable complex compounds with metal ions .

properties

NTA forms stable complexes with metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ or Fe ³⁺ .

use

Structure of the calcium-NTA complex anion

NTA is partially used for water softening . Its use as a softening additive in detergents has declined in recent years, despite the biodegradability of NTA in sewage treatment plants , since the dissolving power of heavy metals is viewed as problematic. In analytical chemistry it is known as complexone I and is used in complexometry to determine metal ions. In 1999, 20,000 tons of NTA were used in Europe.

Use in research

It is also used in affinity chromatography as a chelate ligand (usually with Ni ²⁺ as the central ion) for the purification of poly- histidine - tagged proteins. The purification effect comes about because the polyhistidine binds to the metal of the metal- chelator complex. Examples of suitable metals are nickel, copper or zinc. In the past, iminodiacetic acid (IDA) was mainly used as a chelator. However, this was replaced by NTA in the course of time. In 1987 Ernst Hochuli coupled the NTA ligand to agarose beads for biological research . This Ni-NTA agarose is by far the most frequently used tool to purify His-Tag proteins via affinity chromatography.

Biological importance

It has long been assumed that NTA can mobilize heavy metals from sediment in water bodies . In practice this is not the case, as NTA is present in natural waters as a stable calcium complex. There is a suspicion that this substance is carcinogenic .

proof

NTA can be detected with a copper sulfate solution and a complex indicator.

Individual evidence

1. ↑ ^{a b c d e f} Entry on nitrilotriacetic acid. In: Römpp Online . Georg Thieme Verlag, accessed on April 7, 2014.
2. ↑ ^{a b} Entry on nitrilotriacetic acid in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
3. ↑ Entry on nitrilotriacetic acid in the ChemIDplus database of the United States National Library of Medicine (NLM) .
4. ↑ Sabine A. Lauer, John P. Nolan: Development and characterization of Ni-NTA-bearing microspheres . In: Cytometry . tape 48 , no. 3 , 2002, ISSN  1097-0320 , p. 136-145 , doi : 10.1002 / cyto.10124 .
5. ↑ E. Hochuli, H. Döbeli, A. Schacher: New metal chelate adsorbent selective for proteins and peptides containing neighboring histidine residues. In: Journal of Chromatography A . Volume 411, 1987, pp. 177-184, doi : 10.1016 / S0021-9673 (00) 93969-4 .
6. ↑ Ni-NTA agarose